Incandescent lamp and method of manufacture



1940- R. K. BRAUNSDORFF 2.22.4,855

- INCANDESCENT LAMP AND METHOD OF ANUFACTURE I V Filed April 21, 1938 -INVENTOR say/1M ATTORNEYS I Regina/d K. Braunsdaryf I BY 8m Patented 1 7, 1940 uNrr nv STATES PATENT OFFICE Reginald K. Braunsdorfl', East Orange, N. 1., as-

signor to. Tung-Sol Lamp Works Inc., Newark, N. 1., a corporation of Delaware Application April 21, 1938, Serial No. 203,257

r f 6Claims.

' This invention relates to electric incandescent lamps and to the manufacture thereof.

In the manufacture of filament mounts for miniature incandescent lamps the tungsten fila- 5 ment is often impaired to such an extent that the filament prematurely breaks of! from its support, with the result that the lamp has a useful life substantially less than that for which it was designed. This is particularly true of minor or 10 small filaments of two filament miniature bulbs which are welded and fastened to the nickel support wires by the combination of pressure and heat. This fastening in conventional practice is effected by positioning the, filament end crosswise of the nickel wire and then with one of the relatively movable welding electrodes in direct engagement with the filament end, the latter is pressed into the nickel wire simultaneously with the supply of electric heating current between the electrodes. The nickel support wire in softened or melting in the area of the weld by the electric current and the tungsten wire terminal is readily pressed thereinto .to form a mechanical and electrical connection. Tungsten filaments 5 thus welded and fastened to the nickel wire do not stand up under service conditions the failure to so stand up is believed to be due to the very high temperature to which the tungsten end or terminal is brought during the weld by the passage therethrough of the whole initial volume of current, whereby its, strength is impaired by the disturbance or upsetting of its crystalline structure.

One object of the invention is an incandescent lamp of novel and improved construction and particularly one having a mount of novel and improved construction in which the fila- 'ment is unimpaired during the welding and fastening operations. 40 A further object of the invention is a novel method of welding and fastening the tungsten filament to the nickel wire supports whereby the structure of the filament terminal is unimpaired during the welding and fastening operation. A

. Further objects of the invention will hereinafter appear.

For a better understanding of the invention reference may be had to the accompanying drawing forming a part of this application wherein: Fig. l is a side view of an incandescent lamp embodyingtheihvention: I

Figs. ,2, 3, 4 and 5 are'views illustrating the steps in the mountings! afilament according tothe invention; and

Fig. 6 illustrates a. modification of the invention.

The invention is illustrated as embodied in an incandescent lamp I having a principal filament 2 and aminorfiiament I. The invention will be 5 described .with reference to the welding and fastening of the filament 3 to the nickel wire supports 4. The filament 3 is of tungsten wire and in conventional practice has a diameter of .001 .to .003 inch. The nickel wire supports 4 may be 10 of any suitable size, as for example a diameter of around .022 inch. I

Referring to the modification of Figs. 2 to 5 the first step according to the invention'ls to form a diagonal slot or cut I in the side of the nickel 16 wire 4. The preferred way to form this slot I is by the use of a knife or similar cutting tool or in conjunction with a suitable holding frame or die and this operation results in an upsetting of the outer wall of the diagonal slot I to form.

sten filament 3 within this diagonal slot I crosswise of the support wire 4 and to position the support wire 4 with the filament end I therein" between a movable welding electrode I and a fixedv plate or electrode 8 (Fig. 4). In this posi-. tion and with theparts thus assembled. when the electrode 1 is reciprocated toward the fixed 30 electrode 8 the electrode does not make direct contact-with the filament terminal 3 but, on the contrary, is brought into mechanical and electrical contact only with the nickel wire 4 and the lip or burr 6. beer and press against the support wire 4 with sufiicient pressure to flatten out, the lip or burr 6 and simultaneously therewith a suitable electric heating current is passed between the electrodes I and ,8 of a sufiicient amount to soften or melt 40 the burr or lip 6 about thefiiament terminal! and weld the lip down firmly in position, as indicated in Fig. 5.

A firm weld and fastening of the terminal 3 to the support wire 4 is thus efiected without unduly 45 heating the filament. Very little electric current v if any, passes directly through the filament terminal '3' and the temperature rise therein is that due only to the local heating which takes place in the nickel wire 4 and the up or burr I. The 50 filament I. I is thus unimpaired and its strength and crystalline structure are maintained during the welding and fastening operation. Thenickel I support wires 4. are relativelysoft with the re w suit that when .therelatively movable electrodes 55.

The electrode 1 is then caused to 35 i I .a strip l sides of the wire. 4 under pressure. the edges 4' of the nickel wire 4 which are engaged by the -relatively movable electrodes are slightly fiattened as indicated in Fig. 5.

Figs. 2,.3, 4; and bare, purposely diagrammatic and illustrate the principle-pf the invention; Ihe diagonal slots I may varyin depth and angle and in practice two or more of -the steps illustrated in Figs. 2 to 5 may be performed at the same time or substantially at the same time, as for example by assemblying the filament 3 and the two sup- I port wires 4 on a machine which includes the relatively movable electrodes I and 8 andboth lo terminals 3' of the filaments I may be simultaneously welded to the two nickel wire supports 4. Ordinarily also the movable electrode reciprocates vertically while the support wires 4 are horizontally dispoaed on the fixed electrode or frame & As indicated above, the diagonal slots or cuts I may he formed in any convenient manner, as for example by positlcning the support wires 4 within cylindrical passages of a die or holding frame in which there is provided a diagonal slot or slots leading to the w es and accommodate ing the reception of cutting tools of suitable hardness and cutting edge to form the diagonal slots 5 and upset the lips or burrs G. The filament terminals 3' may be fastened within the slots 5 by bringing'theomovable electrode 1 under high pressure against the side of the support wire 4 including the burr or lip 6, unaccompanied by the supply of electric heating current between the electrodes v1 and 8, but a more satisfactory weld and fastening is efieoted by the simultaneous use of both pressure and electriecurrent. v

In Fig. 8 is illustrated a modification of the invention. Here the filament terminal 8' is asv sembled crosswise of the nickel wire support 4 underneath a strip of nickel ribbon M which is welded at one end II to the nickel wire. The nickel strip ll forms a lip somewhat the lip 0 described above and after the assembly er the terminal I within the gap H (between the strip III and wire 4) the movable electrode 'l is brought down under pressure to the position indicated in dotted lines to weld and fasten the throughout its length to the nickel wire 4 and about the filament terminal 8', as indicated in dotted lines. Anelectric heating current is supplied between the electrodes I and I simuls taneously with the bringing ofv the electrodes is against the wire support 4 and strip II, as described above in: connection with Fig. 4; The nickel strip or ribbon l4 may be of any suitable else, as for example .005 inch by .015 inch, and

as indicated above the support wire 4 may bit-0i "40, any suitable size. as for example aroundbfiil inch diameter.

' The weld and similartoof Fig. Balsa result tlce of Figs. '2, a, 4 and :5 described above is the preferred practice.

I claim:

1. In an incandescent electric lamp, a filament support wire and a filament disposed atan angle thereto having a terminal embedded therein under a lip disposed'on the side thereof, said lip being flattened against and electrically welded to the support wire about the filament terminal with the crystalline structure of the latter unimpaired by the heating current.

2. In an incandescent lamp of the character set forth in claim 1 wherein the lip is formed integrally with and coalesces with the support wire and is flowed around the filament terminal.

3. In an incandescent electric lamp, a filament support wire and a filament disposed at an angle thereto having a terminal embedded therein under a lip disposed on the side thereoi', said lip being flattened against and electrically welded to the support wire about the filament terminal with the crystalline structure of the latter unimpaired by the heating current, the lip being a separate strip or member which is welded at one point to the support wire and coalcsoes with and is flowed around the filament terminal at another point.

4.The method of mounting a filament of an electric incandescent lamp upon mount support wires which includes the steps otassembling the filament terminals underneath lips carried by the 'sides of the support wires and flattening under and beneath the lips and pressing the lips about the filament terminals while simultaneously supplying electric heating current between the lips and the main bodies of the support wire with the lips forming a shunt for the heating current past the terminals.

6. The method of mounting a filament of an electric incandescent lamp upon mount support wires which includes the steps of assembling the v filament terminals underneath lips carried by the sides of the support wiresand flattening under pressure the lips about the terminals of the filament while simultaneously supplying electric heating current through said lips and the main of the support wire to heat the lips and the main bodies to the welding point solely by the passage of current therethrough without the passage of current through the terminals, the lips being formed by welding metallic stripe at' nnomam m'aasonspom. 

